The present invention relates generally to imaging devices and in particular to wavefront angle or wavefront phase sensitive imaging devices.
Conventional digital cameras record light intensity from an illuminated scene, for example, using electronic sensors distributed over a focal plane, to each sense a “pixel” of the image to produce the image. By incorporating colored filters over the electronic sensors, light frequency as well as intensity may be recorded providing colored images.
Conventional digital cameras do not capture important information about the light received from an illuminated scene that may be expressed in the light's wavefront angle or phase. “Light field” or “plenoptic” cameras, however, can capture this wavefront information together with light intensity information providing a more complete representation of the illuminated scene. As a result, such cameras can change the focal distance and depth of field after the image is captured. More generally, the captured wavefront information provides a more complete record of the illuminated scene that may be useful in a variety of applications including postprocessing, image recognition, hologram generation, and the like.
The image sensors using conventional digital cameras, such as charge coupled devices (CCD), do not naturally detect wavefront information but can be modified to produce a Shack-Hartman type wavefront detector. Such modifications place an array of micro lenses in front of a standard image sensor, for example, each micro lens being associated with a two-dimensional zone of multiple pixels of the image sensor. Light received by each micro lens provides a focal spot whose position on the multiple pixels of the zone changes depending on the angle of the wavefront. By detecting which pixels detect the greatest light intensity (indicating the location of the focal spot) the wavefront angle may be deduced. The measured intensity of this focal spot is also used to provide the conventional image intensity information.